Medium 16x16 Sudoku — A Long, Steady Solve

Medium 16x16 sudoku is rated 2.0 to 2.9. Singles still open the puzzle, but they run dry, and from then on you need pairs and line-box moves. It suits players who finish easy grids comfortably and are ready to write candidates down.

What this level asks

Stamina more than cleverness. A row on this board has sixteen cells, so every candidate list is longer than on 9x9 and a missed note costs more time. Medium is where that bookkeeping starts to matter, and where a single sitting often stops being enough. The difficulty levels guide explains the bands.

Techniques you will meet

• Naked and hidden pairs: two symbols confined to two cells of one house, which lets you strike those symbols from the other cells in it. Among sixteen cells a pair is easy to overlook.
• Pointing pairs: a symbol that, inside a 4x4 box, sits in one row or column only, so it can leave the rest of that line.
• Box line reduction: the reverse, where a symbol confined to one box within a line clears the rest of the box.

Pairs matter more on this board than on 9x9 because a house holds sixteen cells: a pair that removes two candidates from fourteen neighbours can unlock several cells at once. Pointing pairs and box line reduction use the 4x4 boxes in the same way, trading information between a box and the row or column it crosses. None of this needs new vocabulary if you already know the 9x9 versions; the patterns are the same, only wider.

Tips for this level

• Write notes only for the box or line where you are stuck, not the whole grid.
• Check boxes before lines. A 4x4 box has fewer cells, so alignments show up there first.
• Update notes after every placement.
• Autosave holds the board between sessions.

Next step

Revisit the basics at easy 16x16, or move on to hard 16x16 once pairs feel automatic.